Fluoride gases (such as NF3, CF4, and C2F6) other than fluorine gas have hitherto widely used in great quantities for semiconductor manufacturing processes because of their high performances. However, because such fluoride gases have high global warming potentials to harm the global environment, it has been decided that the use of them is prohibited or restricted hereafter.
The global warming potential of fluorine gas is zero. Thus, it starts to consider the use of fluorine gas in place of the above-described fluoride gases. However, because fluorine gas is high in corrosiveness and reactivity, it entails risks to transport or store a large amount of fluorine gas with the use of a cylinder. Currently, for those reasons, fluorine gas starts to be used with a cylinder in which fluorine gas has been diluted by 20% or less with inert gas. However, this leads to low efficiency of transportation. In addition, there are also unsolved problems in safeness.
For the above reasons, the industrial world has requested an on-site fluorine gas generator or the like for using fluorine gas on the spot where the gas was safely and stably generated. About it, some proposals have been made. However, although an interface system (fluorine gas supplying system) becomes very important for ensuring consistency of the fluorine gas use quantity and stable supply between the on-site fluorine gas generator and an apparatus that uses fluorine gas, the study of it is scarcely done at present. It has been found that the fluorine gas stable supply and the cost performance of it become a subject of discussion when fluorine gas generated from the on-site fluorine gas generator is supplied to a semiconductor manufacturing apparatus via a fluorine gas supplying system.
In the case of ordinary gas, the above request can be met by a manner that a number of cylinders filled with gas are connected in parallel; a cylinder used is switched to the next cylinder; and the used cylinder is replaced with a new cylinder. Also in the case of fluorine gas, the use of it has been started by a manner that each cylinder is filled with fluorine gas at a low concentration of 20% in consideration of safety; and the cylinders are set in a cylinder cabinet like the case of the above-described ordinary gas. However, because fluorine gas has been diluted by 20%, a large volume is required accordingly and the efficiency of transportation is low. Even in the case of fluorine gas at a low concentration, if a gate valve provided on a cylinder head is broken due to corrosion or the like, there is possibility that the full amount of gas contained in the cylinder leaks out. For these reasons, a supplying method has been desired by which fluorine gas can be supplied safely and stably, and the physical unit of product of fluorine gas is advantageous in comparison with conventional methods. We have hitherto proposed on-site fluorine gas generators that can be used on semiconductor manufacturing spots (generators that can stably supply fluorine gas by controlling the pressure in the generators) (for example, see the below Patent Documents 1 to 3 and so on).    Patent Document 1: Japanese Patent Unexamined Publication No. 2004-107761    Patent Document 2: Japanese Patent Unexamined Publication No. 2004-169123    Patent Document 3: U.S. Pat. No. 6,602,433